A patient may develop side effects of blood transfusion during blood transfusion of a platelet preparation. The plasma that is included in the platelet preparation is regarded as a cause of the side effects. Accordingly, platelets with a low plasma content (washed platelets: also referred to as washed platelet concentrates) are desired at blood transfusion sites.
JP 2013-514863 A discloses a blood apheresis system collecting platelets by performing centrifugal separation on whole blood taken from a donor. The system that is disclosed in JP 2013-514863 A is configured to obtain washed platelets by allowing a platelet-containing component and a platelet additive solution to simultaneously flow into a chamber during the centrifugal separation.